Chain shortening device

ABSTRACT

A chain shortening device is described. The device has the general shape of the letter “C”. A single slot ( 20 ) extends longitudinally along the elongated body ( 10 ) of the device. The single slot has a central widened portion defining a lead-through opening ( 20 E) through which a loop of an associated chain can be inserted, whereby the device can be handled as a separate unit and be attached sideways to an associated chain.

FIELD OF THE INVENTION

The present invention relates to a chain shortening device for use inconnection with associated chains having oblong steel links, the devicebeing of the kind defined in the preamble of claim 1.

BACKGROUND OF THE INVENTION AND PRIOR ART

There are many known chain shortening devices of similar kinds anddesigned to couple two strands (or end portions) of chains together orto shorten a single strand of a chain. Such coupling or shortening isoften desirable for connecting or securing an object to another objector to a fixed support of some kind, or for lifting an object by means ofa lifting device, such as crane, provided with a lifting means, such asa lifting hook or a coupling link, e.g. a master link.

Normally, such a lifting means is connected to two or more chainportions which are coupled to an object to be lifted. Then, it isimportant to shorten at least one of the chain portions, so that theobject is properly balanced during the lifting operation.

A chain shortening device of the kind referred to in the firstparagraph, and which is designed to enable adjustment of the effectivelength of a chain portion, is known from the patent specification DE 4239 482 C2 (Rud-Kettenfabrik). This known device comprises a longitudinalbody having the general shape of the letter “C” and having, at itsarcuate end portions, two pocket-like configurations which merge with anassociated slot portion ending in a widened portion forming an aperture.Thus, there are two such apertures, located on each side of atransversal web joining two parallel side portions of the elongated bodyand serving to permit threading through chain links of a chain coupledto the shortening device so as to adjust the effective length of theassociated chain by positioning selected links in each of thepocket-like configurations. The chain portion between these two suchselected links may either form a slack chain portion of desired lengthor a straight chain portion extending at a small distance sideways fromthe central, normally vertically oriented body part provided with thetransversal web. In this way, the effective length of the chain portioncan be adjusted at will.

However, the structure is such, in particular at the central part of theC-shaped body provided with two different apertures separated by thetransversal web, that the chain portion is trapped in the shorteningdevice (the C-chaped body). In the German patent specification, it isclearly stated that this is an intentional feature (“unverlierbar”approximately meaning “not detachable”), so that the device will notcome apart from the chain and get lost.

OBJECT OF THE INVENTION

The object of the present invention is to provide a shortening device ofthe kind referred to above, which permits a convenient adjustment of theeffective length of a chain portion but which can be handled separatelyfrom the chain. In particular, it should be possible to use theshortening device as a separate unit and couple it to a chain portionwhich is already connected at its ends, e.g. to a lifting means and toan object, respectively.

A further object of the invention is to provide such a separateshortening device, which can be attached sideways to a chain portion soas to be coupled thereto in a safe way with two selected chain linkspositioned in each of the pocket-like configurations.

Another object is to enable an easy adjustment of the effective lengthof a chain portion coupled to the device, so that the adjustment can beeffected conveniently by one person by using his two hands. This shouldbe possible irrespective of the orientation of the device and the chainportion, whether oriented vertically or some other direction.

SUMMARY OF THE INVENTION

These objects are met for a chain shortening device having the featuresdefined in claim 1. Thus, the slot portions of the chain shorteningdevice according to the present invention form parts of a central,single slot extending continuously and longitudinally between the firstand second pocket-like configurations, and this central, single slot hasa widened mid portion forming a central lead-through opening, whichincludes said two apertures and which is dimensioned to permit threadingthrough a loop of said associated chain with two parallel strands. Inthis way, the shortening device can be handled as a separate unit and beattached sideways to an existing associated chain for the purpose ofshortening the effective length thereof. Also, it is easy to adjust theeffective length by moving one of the selected links from the associatedpocket-like configuration of the shortening device to the centrallead-through opening and placing another link into position in thecentral lead-through opening, whereupon this other link can be displacedinto the pocket-like configuration, where it is safely coupled to theshortening device.

Preferably, the central lead-through opening is elongated in thelongitudinal direction of the elongated body. The width of the slotportions adjacent to the central lead-through opening should be onlyslightly wider than said material thickness d of the links of theassociated chain, such as to prevent coupling to a chain consisting oflinks being stronger than those of the associated chain, and the lengthof the central lead-through opening should be such as to permitthreading through a loop of an associated chain with the links of thetwo parallel strands of the loop being positioned next to each other inthe longitudinal direction of the elongated body of the shorteningdevices.

Most preferably, the central lead-through opening should be wider thanthe outer width of the links of the associated chain and longer than 1,5times that width.

In a modified embodiment according to the invention, the centrallead-through opening has, at the mid portion of the elongated body, awaist portion with a reduced width so as to permit threading through acentral part of an upright link forming the leading end of a loopthrough said waist portion and threading through the adjoining parallelstrands through wider apertures on each side of said waist portion.

Additional advantageous features will appear from the detaileddescription below, and some of these features are defined in thedependent claims appended to this description.

Accordingly, the invention will be explained more fully below withreference to the drawings illustrating some preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show a first embodiment of a shortening device of theinvention and, in dashed lines, a portion of an associated chain, in arear view (from the left in FIG. 1B) and a central sectional view,respectively;

FIGS. 2A and 2B show, in views corresponding to FIGS. 1A and 1B, asecond embodiment of the shortening device;

FIGS. 3A, 3B, 3C, 3D, 3E, and 3F illustrate, in schematic side views,how the shortening device can be used together with an associate chainprovided with coupling and hook means at its ends;

FIGS. 4A and 4B show, in schematic perspective views, how the shorteningdevice can be used together with four chain portions for lifting anobject;

FIG. 5 shows, in a sectional view, how a loop of an associated chain canbe threaded through the first embodiment of the shortening device;

FIG. 6 shows, likewise in a sectional view, the first embodiment of theshortening device being coupled to the associated chain so as to shortenthe effective length of the latter;

FIG. 7 illustrates, likewise in a sectional view, an operation servingto adjust the effective length of the associated chain coupled to thefirst embodiment of the shortening device.

FIG. 8 shows, in a view corresponding to FIG. 1A, a modified version ofthe first embodiment with alternative retainer members; and

FIGS. 9A and 9B illustrate, in views corresponding to FIGS. 1A and 1B, athird embodiment of the shortening device.

The first embodiment of the shortening device, shown in FIGS. 1A and 1B,comprises a unitary body 10 of forged steel. The elongated body 10 iselongated in a longitudinal direction D, which also forms the centrallongitudinal axis of an associated chain being coupled to the body 10.The elongated body 10 has the general shape of the letter “C”, as seenin the sectional view of FIG. 1B, including a vertically extending midportion 11, an upper or first end portion 12 and a lower or second endportion 13 (“upper” and “lower” is only related to the position as shownin the drawings and not necessarily in use of the device). Each of theend portions 12 and 13 has an arcuate or bent portion 12A, 13A formingthe transition between the straight mid portion 11 and the likewisestraight portions near the respective free ends of the body 10. Thesearcuate or bent portions 12A,13A could alternatively be formed at theupper and lower portions of the mid portion 11. In the shownembodiments, the end portions 12,13 are directed obliquely upwardly anddownwardly respectively, so as to diverge from each other and form awide space therebetween. This wide space is useful when handling thechain portion located between these end portions.

As will be apparent from FIG. 1A, the body 10 is longitudinally dividedinto two parallel side parts 10A and 10B extending at a respective sideof the longitudinal axis D and being mutually connected to each other ateach end 12B and 13B, respectively (FIG. 1B). The two side parts 10A and10B form between themselves a central, single slot 20 extendinglongitudinally and continuously from the upper or first end 12B to thelower or second end 13B of the body 10.

Adjacent to the upper or first end 12B, the side parts 10A and 10B oneach side of the slot 20 form a pocket-like configuration 20A withseating surfaces curved and dimensioned so as to support a selected linkL2 and its adjoining links L1 and L3 of an associated chain coupled tothe shortening device. The links L1-L5 of the associated chain areoblong having an outer length l and an inner length p, an outer width wand a material thickness or diameter d.

The side parts 10A and 10B, adjacent to the lower end 13B, form acorresponding lower or second pocket-like configuration 20B for aselected link 16 and its adjoining links L5 and L7. In FIGS. 1A and 1B,the links L2 and L6 are selected to be positioned in first and secondcoupling positions in the first and second pocket-like positions,respectively, and the links L3, L4, L5 located therebetween form astraight line along the longitudinal axis D. As will be described below,it is possible to adjust the mutual coupling between the device and theassociated chain, so that a slack chain portion will instead be arrangedbetween the two pocket-like configurations 20A,20B (see FIG. 6).

The single central, longitudinally extending slot 20 includes first andsecond (upper and lower in the drawings) slot portions 20C and 20Dextending from the respective pocket-like configuration to a central,widened opening 20E. The first and second slot portions 20C, 20D have awidth which is only slightly wider than the material width w of thechain links so as to give a convenient clearance when displacing a chainlink along the slot portion while being oriented with its central planelocated centrally in the slot through the longitudinal axis D.

Each slot portion 20C,20D merges with the central opening 20E via aslightly diverging mouth portion 20C′, 20D′. The central opening 20E iselongated in the longitudinal direction D. In the preferred embodimentas shown, the width of the opening 20E is slightly wider than the widthw of the chain links and the length of the opening 20E is longer thanthis width w. Preferably, its length is between 1.5 and twice this widthw. Hereby, a loop of the chain can be threaded through the opening 20Eas illustrated in FIG. 5.

The side parts 10A and 10B of the elongated body 10 are provided withcurved recesses adjacent to the central slot 20, as is previously knownper se in similar devices, so that the links adjoining a link in theslot are accommodated with their curved end portions in these recesseswhile being displaced along the respective slot portion to the first andsecond pocket-like configurations 20A and 20B, respectively.

In the vicinity of each mouth portion 20C′,20D′ of the slot 20, theelongated body 10 is provided with retaining members in the form oftransverse pins 30A and 30B, which are guided in associated transversebores 31A and 31B, respectively, in the side part 10 b of the elongatedbody 10. The pins 30A and 30B are movable between a locking position, asshown, and a retracted position (not shown) against a helical springmember 32A and 32B, respectively. The retaining members 30A, 30B serveto retain a selected chain link L2, L6 in each slot portion 20C, 20D, sothat the chain remains coupled to the shortening device.

An alternative embodiment of such retaining members is shown in FIG. 8.Here, the elongated body 10″ corresponds essentially to the embodimentof FIGS. 1A and 1B. The transverse retainer pins 30′A and 30′B are notspring-loaded but are held in retaining positions by means of lockingpins 32′A and 32′B. These locking pins 32′A and 32′B are inserted intoassociated bores (perpendicularly to the retaining pins) and are securede.g. by friction, threads or conical clamping.

However, the main purpose and advantage with the shortening device ofthe present invention is to permit attachment of the shortening device,being a separate unit 10, to a chain unit 40 (FIG. 3A) which isconnected at its ends to a respective connecting means, such as a masterlink 50 and a hook 60. The shortening device can thus be positioned atany convenient location between the ends of the chain, whereupon a loop41 of the chain 40, with two parallel strands 42,43 (see FIG. 3B andFIG. 5), is drawn through the central opening 20E. A selected link L2 isbrought into the upper or first slot portion 20C (FIG. 7) and ispositioned in the upper or first pocket-like configuration 20A of thebody 10.

Thereupon, the operator grabs the chain links on each side of theshortening body 10 with his (or her) hands LH, RH (FIG. 3C) and pullsthrough the chain loop through the central opening 20E (FIG. 7) until aselected link L12 is positioned in alignment with the lower or secondslot portion 20D. This lower selected link L12 is then manuallydisplaced through the slot portion 20D all the way down to the lower orsecond pocket-like configuration 20B. The final, coupled position of thechain 40 with a slack chain portion 45 is shown in FIGS. 3D and 6. Inthis position, the retainer pins 30A, 30B (FIG. 1A) are inserted intotheir locking positions to secure a safe coupling of the shorteningdevice 10 to the chain unit 40. Of course, the length of the slack chainportion 45 can be chosen at will so that the effective length of thechain unit 40 obtains a desired length.

The orientation of the chain unit 40 is not important. In FIG. 3F, theassembly of FIG. 3D is shown upside down with the hook 60 at the top andthe master link 50 at the bottom.

It will be apparent that the chain unit 40 can be adjusted to anydesired effective length, by an operation similar to the one illustratedin FIGS. 3B, 3C and 3D. This also includes the possibility of lettingthe chain unit 40 form a totally straight line, as shown in FIG. 3E andcorresponding to the configuration illustrated in FIGS. 1A and 1B.

The elongated body 10 should be dimensioned not only to conform to thematerial thickness d and outer width w of each chain link L1, L2, etc.but also to the inner length p of each chain link of the associatedchain, so that an odd number of links (e.g. the links L3, L4 and L5) canbe positioned along a straight line D between the first and secondpocket-like configurations accommodating the selected links L2,L6.Preferably, the length L between the seating surfaces A and B facingeach other at the longitudinal axis D should be approximately:L=n×p+qwhere

-   -   n is an odd integer >0    -   p is the inner length of each chain link,    -   0<q<3.5d, and    -   d is the material thickness of each chain link.

Preferably, the distance q=2.2d as shown in FIGS. 1A and 1B. However,the distance q could be slightly longer, up to 3d, or shorter than showndown to 2d. With such dimensional limits of the shortening device, it ispossible to let the chain links take the full load without transferringany part of the load to the shortening device when the chain is arrangedas a straight chain portion along the longitudinal axis D while stillbeing coupled to the shortening device (as shown in FIGS. 1A, 1B and 3E.Furthermore, the limit q=2d is a necessity for n=1. Hereby, it ispossible to use the chain to its full strength (although only at fulllength) without having to detach the shortening device from the chain.

FIGS. 4A and 4B illustrate how the chain shortening device 10 can beused when lifting a box-like object O by means of four chain portionsC1, C2, C3 and C4 connected at the top to a master link 50 and at thebottom to four corners of the object O. Two of the chain portions, C1and C2, are provided with chain shortening devices. By adjusting theeffective lengths of these chain portions, it is possible to balance theorientation of the object, even if the corner points are locateddifferently for different objects, as illustrated in FIGS. 4A and 4B. Incase, there are only two or three chain portions connected to a masterlink 50, it is generally sufficient to adjust the length of only onechain portion, in particular by means of the attachable and detachablechain shortening device according to the invention. It is possible toattach one or more chain shortening devices without detaching the chainportions from the master link or from the load.

A second embodiment of the chain shortening device is shown in FIGS. 2Aand 2B. The elongated body 10′ is shorter and has no retainer members.Its length between the opposite seating surfaces A and B is slightlylonger to one link (n=1 in the above formula). Also, the centrallead-through opening 20E′ is somewhat shorter as compared to FIGS. 1Aand 1B. Otherwise, this embodiment is substantially like the firstembodiment.

Of course, it is also possible to have a longer body 10 than the firstembodiment of FIGS. 1A and 1B. This first embodiment is veryadvantageous in terms of strength, relative low weight and easy manualhandling. In this respect, it should be noted that the overall weightand strength is improved by the diverging free end portions as comparedto an embodiment as disclosed in the above-mentioned German patentspecification (with mutually parallel free end portions of the body).

A third embodiment of the chain shortening device is shown in FIGS. 9Aand 9B. Here, the elongated lead-through opening 20′″E is provided witha waist portion 22 located in the mid portion of the elongated body10′″. The waist portion 22 has a reduced width w′″ which is smaller thanthe outer width w of the associated chain links. In this way, twoapertures 20′″F and 20′″G are formed on each side of the waist portion22, these two apertures 20′″F, 20′″G communicating with each other. Suchan embodiment works very well. An end link L0 of a loop 41 of a chaincan be threaded through the opening 20′″E in upright position.Thereupon, the parallel strands 42,43 of the loop 41 can be pulledthrough the respective apertures 20′″F, 20′″G. Because of the shape ofthe opening 20′″E, the two strands 42,43 are guided smoothly in therespective aperture 20′″F, 20′″G and prevents the strands from beingtwisted.

1. A chain shortening device in combination with an associated chainconsisting of oblong links having a material thickness d, an outer widthw and an outer length 1 which is longer than said outer width w, saidchain shortening device comprising: a unitary elongated generallyC-shaped body with a mid portion and two free end portions, and firstand second slot portions located at the free end portions of the “C”,each of said slot portions including a first and a second pocket-likeconfiguration, respectively, for positioning selected links of saidassociated chain in a first and a second coupling position,respectively, and each of said first and second slot portions having,adjacent to said pocket-like configuration, a width which is wider thanthe material thickness d of said chain links but narrower than the outerwidth w of said chain links, and adjacent to a mid portion of saidelongated body, a widened slot portion defining a respective one of twoapertures, which are wide enough to permit threading said associatedchain through said aperture, so that, upon coupling said associatedchain to the shortening device with two selected links located in saidfirst and second coupling positions, respectively, the chain linkslocated between the two selected links will form either a straight chainportion, extending at the side of said mid portion of the elongated,generally C-shaped body, or a longer slack chain portion enabling theeffective shortening of said associated chain, wherein said slotportions form parts of a central, single slot extending continuously andlongitudinally between said first and second pocket-like configurations,and said central, single slat has a widened mid portion forming acentral lead-through opening, which includes said two apertures andwhich is dimensioned to permit threading through a loop of saidassociated chain with two parallel strands, whereby the shorteningdevice can be handled as a separate unit and be attached sideways to anexisting, associated chain for the purpose of shortening the effectivelength thereof.
 2. A combination as defined in claim 1, wherein saidcentral lead-though opening is elongated in the longitudinal directionof said elongated body.
 3. A combination as defined in claim 2, whereinthe width of the slot portions adjacent to the central lead-thoughopening is only slightly wider than said material thickness d of thelinks of the associated chain, so as to prevent coupling of theshortening device to a chain consisting of links being stronger thanthose of the associated chain, and the length of central lead-throughopening is such as to permit threading through a loop of an associatedchain with the links of the two parallel strands of the loop beingpositioned next to each other in the longitudinal direction of theelongated body.
 4. A combination as defined in claim 3, wherein saidcentral lead-through opening is wider than said outer width w of thelinks of said associated chain and longer than 1.5 times that width w.5. A combination as defined in claim 1, wherein said centrallead-through opening has, at said mid portion of said elongated body, awaist portion with a reduced width, which is less than the outer width wof said chain links but greater than the material thickness d of saidchain links, said waist defining said two apertures on opposite sidesthereof so as to permit threading through a central portion of anupright link forming the leading end of said loop of said chain throughsaid waist portion and threading though the adjoining parallel strandsthrough said two apertures.
 6. A combination as defined in claim 5,wherein each of said apertures are wider than said outer width w of saidchain links but shorter, in the longitudinal direction of said elongatedbody, than said outer width w.
 7. A combination as defined in claim 1,wherein retainer members are located in each of said first and secondslot portions so as to selectively retain said first and second selectedlinks adjacent to said first and second coupling positions.
 8. Acombination as defined in claim 1, wherein said free end portions ofsaid elongated body are directed obliquely away from each other.
 9. Acombination as defined in claim 1, wherein seating surfaces, which formparts of said pocket-like configurations and face towards each other,are located at a mutual distance L from each other, said distance LbeingL=n×p+q where n is an odd integer>0 p is the inner length of each chainlink of the associated chain, 0<q<3.5d d is the material thickness ofeach chain link.
 10. A combination as defined in claim 9, wherein2d<q<3d.